United States Patent (19) [11] Patent Number: 4,966,237 Swanson et al. 45) Date of Patent: Oct. 30, 1990

(54 METHOD OF EFFECTING EXPANDING 56 References Cited CHEMICAL ANCHOR/SEALS FOR ROCK U.S. PATENT DOCUMENTS CAVTES 2,939,533 6/1960 Coberly ...... 166/285 X 75 Inventors: David E. Swanson, West St. Paul; 2,986,217 5/1961 Johnston .. ... 166/285 X Michael X. Schlumpberger, Eagan, 3,583,165 6/1971 West et al...... 405/266 both of Minn. 3,878,686 4/1975 Hageman et al...... 405/264 3,995,694 12/1976 Frieburger ...... 166/285 4,002,483 1/1977 Daugherty et al. . ... 106/89 (73) Assignee: The United States of America as 4,252,474 2/1981 Botes ...... 405/266 represented by the Secretary of the 4,328,036 5/1982 Nelson et al...... 166/293 X Interior, Washington, D.C. 4,537,535 8/1985 MacBain ...... 405/260 4,797,159 A1989 Spangle ...... 166/292 X (21) Appl. No.: 383,111 Primary Examiner-George A. Suchfield 22 Filed: Jul. 20, 1989 Attorney, Agent, or Firm-E. Philip Koltos (51) Int. Cl...... E21B33/138; E21B 43/26; 57 ABSTRACT E02D 3/12 Method of sealing a cavity formed in a rock against the (52) U.S. C...... 166/292; 166/281; passage of fluids without fracturing the rock, by placing 405/263; 405/266 wadding in the cavity and adding a supply of expanding 58 Field of Search ...... 405/260, 263,266, 267, chemical grout to effect a seal upon hardening. 405/269; 166/281, 285,287,292, 293,294, 295; 106/89 10 Claims, 1 Drawing Sheet

U.S. Patent Oct. 30, 1990 4,966,237

N&SS3\g 3.ŠS2

3.

4,966,237 1. 2 strength bolt is embedded within the grout for anchor METHOD OF EFFECTING EXPANDING ing in place after the grout expands. CHEMICAL ANCHOR/SEALS FOR ROCK FIG. 3 depicts a cross section of a cavity in a rock, CAVTES wherein high-pressure tubing and wadding are together positioned within a cavity and expanding grout is FIELD OF THE INVENTION placed above the wadding and around a section of the The invention relates to a method of effecting chemi tubing to function as a high pressure injection seal. cal anchor seals for cavities formed in rock such as DETAILED DESCRIPTION OF THE boreholes, wells and fissures, against the passage of INVENTION fluids. 10 The invention employs grouting compounds of the BACKGROUND OF THE INVENTION non-explosive demolition type, such as S-Mite (R) and In the fields of mining, petroleum production, civil Bristar (E) for sealing a hole formed in a rock structure, and geological engineering, and construction, there is a anchoring an object in a cavity formed in a rock or need to improve sealing techniques, which are domi 15 effecting a high pressure seal about a conduit placed in nated by the use of cements, epoxies and liquid prod a rock cavity for purposes of injecting fluids under ucts; however, these seals are attendant with many pressure. Typically, the S-Mite (R) formulation is as difficulties when it comes to either the effectiveness of follows on a weight basis: the seal or the ability of the seal to withstand high pres sure without the passage of fluids. 20 In the process of effecting anchoring or sealing, liquid SiO2 0.6% Al2O3 0.5% products that harden subsequent to emplacement in a Fe2O3 1.6% cavity have one or more of the following drawbacks: CaO 89.1% inadequate sealing due to shrinkage during curing, in MgO 1.7% sufficient adhesion, inability to respond to minor defor 25 SO3 .01% trace mation of the surrounding cavity, and gravitationally Ignition Loss 6.5% induced flow away from upper surfaces in the case o horizontally aligned cavities. In FIG. 1, there is depicted a cross section of a cavity On the other hand, expanding chemical grouts have in a rock, wherein wadding 3, is positioned within cav been commercialized to make non-explosive demolition 30 ity 1, and expanding grout 2, is emplaced above the agents, however, manufacturers of expanding chemical wadding to effect a seal. non-explosive demolition agents caution that these It is critical to the invention that the expanding grout, agents must be used for their designated purposes of which may be liquid when emplaced, fills the intended either fracturing rocks or fracturing concrete. In such a sealing area as the grout hardens. Failure to do so may fracturing process, any seal which may have been pro 35 visionally effected is also shattered. result in inadequate seal formation. Therefore, a need exist in all of the aforementioned EXAMPLE 1. areas for a method which will effect a seal by using a About 20% water and about 80% dry grouting com chemical grouting material when it is desired not to pound on a weight basis were mixed together. Within fracture or demolish rock structures having cavities 40 10 minutes after mixing, the expanding grout mixture therein. was placed within a hole in rock as shown in FIG. 1, SUMMARY OF THE INVENTION with the exception that no wadding was previously In accordance with the present invention, a method placed in the hole. The emplacement of the expanding has been devised for sealing a cavity in a rock formation 45 grout mixture was found to be inadequate, because against passage of fluids without fracturing walls of said without the wadding, the fluid grout mixture was gravi cavity, by placing in said cavity, a material capable of tationally induced to flow away from the intended seal confining the flow of a supply of a hardenable and voi ing area of the hole, causing the expanding grout mix ume expandable chemical grout which occupies a given ture to relocate to the bottom of the hole in the rock. volume in its initial unhardened and unexpanded condi 50 With this deficient emplacement of the expanding grout tion, and an increased volume relative to said given mixture, an inadequate seal was formed in the intended volume in its hardened condition, to exert an expansive sealing area and flow of materials past the intended force against confining surfaces; adding into said cavity sealing area was not prevented. and against said material capable of confining the flow, When confined, non-explosive demolition agents a hardenable and volume expandable chemical grout 55 such as "S-Mite' and "Bristar' generate expansive material adapted to exert pressure and effect an ex stress that increase with time. It is also critical to the panded seal upon curing, between confining surfaces of invention that the expanding grout not fracture the the cavity and the material capable of confining the surrounding structure of the cavity because the grout flow of the grout. will not harden without confinement and the grout seal 60 may not be effective if cracks are created in surrounding DESCRIPTION OF THE DRAWINGS structure after the grout has hardened. Unless control FIG. 1 depicts a cross section of a cavity in a rock, ling measures are taken, the expanding grout mixture wherein wadding is positioned within the cavity and an may fracture the surrounding structure within the in expanding chemical grout is placed above the wadding tended period of use. to effect a seal. 65 FIG. 2 depicts a cross section of a cavity in a rock, EXAMPLE 2 wherein wadding is positioned within the cavity, ex Same as Example 1 with the exception that wadding panding grout is placed above the wadding, and a high was used to contain a supply of the expanding grout 4,966,237 3 4. mixture in the intended sealing area. The expanding pressure required to make the seal fail. For 24 hour grout mixture was placed in the intended sealing area curing times, the results demonstrated that a 2 inch long and was restrained from gravitationally induced flow seal will fail at about 13,000 psi water pressure and that by the wadding. After about 6 hours from the time of a 4-inch long seal will exceed the 20,000 psi capability of mixing the expanding grout mixture was transformed 5 the test equipment used. from its initially fluid condition to that of a partially FIG. 2 shows a cross section of a cavity in rock, hardened cement and started generating expansive wherein a high strength bolt 14, and wadding 13, are stresses against the confining walls of the surrounding positioned together within the cavity 10, and expanding rock, enabling the formation of a seal. With passage of grout 12, is emplaced above the wadding and around a time, continued generation of expansive stress by the 10 section of the bolt in order to anchor the bolt in place expanding grout mixture strengthened the seal. How after the grout expands. ever, after about 3 days, the additional generation of expansive stress eventually fractured the surrounding EXAMPLE 5 rock structure with cracks radiating from the hole into Same as Example 4 with the exception that a steel the rock structure. The cracks radiating from the hole 15 bolt was used in the manner shown in FIG. 2 in order to into the rock structure presented a path for movement anchor the bolt in place after the grout expands. The of materials around the hardened expanding grout mix bolt was pushed through the wadding, the bolt and ture and destroyed the seal created by the expanding wadding were positioned together within the steel cyl grout mixture. inder, and the expanding grout mixture was placed 20 above the wadding and around a section of the bolt. EXAMPLE 3 Using a 1.0 inch outside diameter bolt and a 1.8 inch Same as Example 2 with the exception that the ex inside diameter cylinder, the expanding grout mixture panding grout mixture was about 20% water, 40% was placed above the wadding and around a 6.6 inch grouting compound, and 40% of fine silica sand by long unthreaded section of the bolt, causing the bolt to weight. With the expanding grout mixture confined 25 resist 50,000 pounds of pull-out force when later tested. from gravitationally induced flow by the wadding, the FIG. 3 depicts a cross section of a cavity in rock, expanding grout mixture filled the intended sealing area wherein high-pressure tubing 24, and wadding 23, are as a fluid. After about 6 hours after mixing, the expand positioned together within the cavity 20, and the ex ing grout mixture was transformed from its initially panding grout 22, is emplaced above the wadding and fluid condition to that of a partially hardened cement 30 around a section of the tubing in order to anchor the and started generating expansive stresses against the tubing in place and effect a high-pressure injection seal. confining walls of the surrounding rock enabling the For high pressure fluid injection seals that require formation of a seal. With passage of time, continued only a few hours of working life and fragmentation of generation of expansive stress by the expanding grout the surrounding structure is not a concern, expanding mixture strengthened the seal. With additional passage 35 grout mixtures that are capable of eventually fracturing of time, additional generation of expansive stresses did the surrounding structure may be used. This is espe not fracture the surrounding rock and the seal created cially applicable to the use of the methodshown in FIG. by the expanding grout mixture remained intact. 3 for hydraulic fracturing of the surrounding structure For materials that are beyond the fragmentation ca by means of high pressure fluid injection. pabilities of non-explosive demolition agents such as "S-Mite' and "Bristar,' the method of the invention EXAMPLE 6 shown may be used without diminishing the expansive Same as Example 2 with the exception that high pres capabilities of the grout to achieve an effective seal over sure stainless steel tubing was used in the manner shown a long duration. in FIG. 3 in order to anchor the tubing in place and 45 effect a high pressure injection seal after the grout EXAMPLE 4 Using 0.562 outside diameter and a 0.1875 inch inside Same as Example 2 with the exception that wadding diameter stainless steel tubing, the tubing was pushed in the form of foam rubber and expanding grout mixture through the wadding, and the tubing and wadding were were placed in 20,000 psi rated stainless steel cylinder positioned together within a 1.5 inch internal diameter instead of a hole in rock. With the expanding grout 50 bore hole in dolomite rock, and the expanding grout mixture confined from gravitationally induced flowage mixture was placed above the wadding and around a six by the wadding, the expanding grout mixture filled the inch long section of the tubing. After allowing the ex intended sealing area as a fluid. After about 6 hours panding grout mixture to cure for about 18 hours, fluid from the time of mixing, the expanding grout mixture injection pumping through the tubing into the confined was transformed from its initially fluid condition to that 55 cavity in the dolomite indicated not only that the tubing of a partially hardened cement and started generating was securely anchored, but also that the tubing was expansive stresses against the confining walls of the sealed in place. Injection pressures prior to hydraulic surrounding stainless steel cylinder, enabling the forma fracturing of the dolomite were as high as 11,000 psi tion of a seal. With passage of time, continued genera with no evidence of seepage by the seal. tion of expansive stress by the expanding grout mixture For high pressure fluid injection seals that require a strengthened the seal. However, with additional pas long working life or where the fragmentation of the sage of time, the additional generation of expansive surrounding structure is a concern, expanding grout stress did not fracture the surrounding high pressure mixtures that are not capable of eventually fracturing rated cylinder and the seal created by the expanding the surrounding structure may be used. grout mixture remained competent. 65 Using such a seal as described in Example 4, more EXAMPLE 7 than 250 individual tests with varied curing time and Same as Example 3 with the exception that high pres length of seal were performed to determine the water sure stainless steel tubing was used in the manner shown 4,966,237 5 6 in FIG. 3 in order to anchor the tubing in place and faces and generates stresses against surfaces that restrict effect a high pressure injection seal after the grout ex further expansion. pands. The tubing was pushed through the wadding, the With continued hydration and stress generation, the tubing and wadding were positioned together within grout hardens and is anchored in place by a combina the cavity in rock, and the expanding grout mixture was tion of mechanisms. Under these conditions, expanding placed above the wadding and around a section of the chemical grouts become impermeable to fluids and form tubing. Using a 0.562 inch outside diameter and 0.1875 a fluid seal against the confining surfaces. These anchor inch inside diameter stainless steel tubing in a 1.5 inch ing and sealing capabilities are maintained as long as the internal diameter bore hole in dolomite rock, the ex cavity resists the expansive forces exerted by the grout, panding grout mixture was placed above the wadding O which should not be so great as to fracture the cavity and around a 6 inch long section of the tubing. After encompassing material. allowing the expanding grout mixture to cure for about Using the method of the invention, it is believed that 4 weeks, the tubing was securely anchored and there the expanding grout behaves as a visco-plastic, starting was no evidence of fracturing in the rock surrounding as a viscous fluid and transforming to a hardened solid, the bore hole. 15 (with an intermediate putty stage). The transformation It is clear that, for anchoring and sealing in the art to from viscous fluid to hardened solid is due in part to the date, the drawbacks of inadequate sealing due to shrink removal of free water from the slurry and chemical age during curing, insufficient adhesion, inability to incorporation of water into hydrated crystals. Through respond to minor deformation of the surrounding cav this incorporation of water in hydration, the total vol ity, and gravitationally induced flow away from upper 20 ume of solids and liquids may decrease, and yet the surfaces in horizontally aligned - cavities have been overall mass may expand as a result of the manner of solved by the method present invention, through expan crystal growth. The product of hydration would be a sion and stress applied to confining surfaces. Because porous and friable powder, if not for the confinement the method of the invention uses an expanding grout, pressure. shrinkage and other difficulties ensuring proper surface 25 Expansive stress is generated as the grout sets. Before contact are overcome. The method of the invention setting, the grout is free to expand in a direction of anchors with friction in addition to adhesion and non-confined boundaries. As the grout hardens, expan greatly improved anchoring is thus obtained. This is sion in the direction of nonconfinement is inhibited by especially important in applications where adhesive anchoring within the cavity. This explains why expand bonding alone is inadequate. 30 ing grouts confined on as few as two sides are able to In using expanding chemical grouts in accordance generate stresses exceeding 100 MPa. However, the with the method of the invention, the material encom magnitude of expansive stress generated near non-con passing the cavity is not demolished. To the contrary, fined boundaries is reduced by the inadequacy of local the integrity of the confining cavity is essential to the 35 ized anchoring. This reduction is generally restricted to function of the invention, because the cavity must pro within a distance equivalent to the cavity's minor diam vide continuing resistance to expansive stress generated eter at the non-confined boundary. by the expanding grout for the maintenance of seals and The anchoring mechanisms will include surface adhe anchors. sion, static friction, and mechanical interlocking of the Therefore, the present invention provides methods mating contours of the cavity, imbedded objects and the of: (1) sealing cavities; (2) anchoring objects within hardened grout. The surface adhesion is similar in prin cavities; (3) coupling fluid conveying devices to a cav cipal to that of hard water scale accumulation in pipes. ity which lacks conventional fasteners such as threads; The magnitude of the static friction depends on the and (4) reduces the cost and complexity of some diffi pressure exerted by the grout, the area over which cult anchoring and sealing applications such as when 45 pressure is exerted, and the coefficient of static friction the cavity is irregular, deformable under stress, or com between the grout and the cavity. Regarding both sur posed of weakly cemented materials. face adhesion and static friction, it is clear that, the A wide variety of barriers to movement (such as larger the area of contact between the grout and cavity, seals, anchors and couplings) within cavities (such as the greater the anchor and sealing capabilities. In regard pipe or tubing, wells, boreholes in rock, and fissures) is 50 to mechanical interlocking, it should be apparent that thus insured on the closure or plugging, anchoring, and the anchoring capabilities increase with increasing con coupling using the invention method. tour roughness of surfaces that confine the grout. While the calcium oxide chemical grouts used ac However, it should be noted that the cavity must tively combine with water in a manner that causes them provide continuing resistance in order to maintain the to expand, it should be understood that other grouts will 55 expansive stress generated by the expanding grout. also work; however, while the expansion of calcium Without this stress, the grout would have no frictional oxide through hydration is only apparent in bulk, the anchoring and the hardened grout would be free to volume of slaked lime is actually less than the sum of the slake into a loose, friable solid. Minor deformation of volumes of the quick lime and water used in the reac the cavity during initial grout expansion or later loading tion. The particles of hydrate grow preferentially in against the grout does not preclude the successful use of certain orientations as hexagonal plate crystals, thrust the invention, as the grout expansion will continue and ing particles apart and producing an expansion due to make up for the increased volume. less efficient packing than non-hydrated crystals. Thus, In sealing or anchoring the expanding grout mixture it is believed that the grouts using the invention method is blended to have the desired physical properties for expand as the result of chemical hydration and accom 65 the application, such as viscosity, reaction rate, and panying crystal growth. When prepared and emplaced magnitude of expansive stress generated. in accordance with the invention method, swelling of The viscosity of the mix can be controlled by the the expanding grouts ensures contact with cavity sur relative proportions of wet and dry components. Addi 4,966,237 7 8 tionally, the mix will thicken with time after the addi a given volume in its initial unhardened and unex tion of water as a result of the hydration. panded condition, and an increased volume relative The rate of the hydration reaction can be controlled to said given volume in its hardened condition to by such factors as the chemical composition of the hy exert an expansive force against confining surfaces; drating crystals, the size of the hydrating crystals, ag and glomeration of the hydrating crystals, the addition of adding into said cavity and against said material capa catalyst reagents to the grout mixture, and the tempera ble of confining the flow, a hardenable and volume ture under which hydration takes place. expandable non-explosive demolition chemical The stress generated by the reaction can be con grout material adapted to exert pressure and effect trolled by such factors as the chemical composition of 10 an expanded seal upon curing between confining the hydrating crystals, the amount of water in the hy surfaces of the cavity and said wadding material drating grout-water mixture, the dimensions of the cav capable of confining the flow. ity into which the hydrating grout-water mixture is 2. The method of claim 1, wherein said wadding emplaced, the proportion of inert additives added to the material capable of confining the flow of said grout is hydrating grout water mixture, and the extent of hydra 5 selected from fabric, casing, foam rubber, rags and tion that occurs before the grout is confined in a cavity. paper towels. Expanding grout is prepared in the manner of mixing 3. The method of claim 2, wherein said chemical Portland cement by mixing dry compounds or a com grout is obtained by: admixing about 20% by weight of mercially available demolition grout with water. water with about 80% by weight of a grouting composi In a down angled cavity, expanding grout is poured 20 to the desired depth and then left to expand and gener tion composed of: ate the seal. In applications where pouring is not possi ble, the grout may be emplaced by pumping or packing. SiO2 0.6% Wadding is positioned in the cavity to control the Al2O3 0,5% 25 Fe2O3 1.6% excursion of emplaced expanding grout. Foam rubber, CaO 89.1% rags casing, and paper towels are preferred as the wad MgO 1.7% ding material, but a wide range of additional materials SO3 .01% (trace) are suitable. In a vertically oriented cavity, the grout Ignition Loss 6.5% can be emplaced above wadding capable of supporting the weight of the grout. In a horizontally oriented cav 30 4. The method of claim 1, wherein a barrier to fluid ity, grout can be placed against wadding. movement is created within the cavity by expansion as When anchoring objects within cavities, after prepar result of a hydration reaction and accompanying crystal ing an expanding chemical grout in the manner de growth to create a seal. scribed for sealing a cavity, an object is emplaced 5. A method of anchoring an object in a cavity such within the cavity prior to the addition of the expanding 35 as a bore hole, well, or fissure without fracturing walls chemical grout or set into the grout filled cavity soon of said cavity, comprising: after the emplacement of the grout. After the grout is emplaced in the cavity around the object and the grout placing in said cavity, a wadding material capable of is given time to set and expand, the object within the confining the flow of a supply of a hardenable and grout will be anchored. volume expandable chemical grout which occupies Devices such as washers may be used to assist in a given volume in its initial unhardened and unex positioning articles within the expanding grout before panded condition, and an increased volume relative hydration is advanced i.e. to position anchor rods away to said given volume in its hardened condition to from cavity walls. exert an expansive force against confining surfaces; Objects anchored within the cavity and protruding placing an object within the cavity in a manner such outward may facilitate mechanical coupling between that said object extends through the material capa the cavity and other external articles. Threaded rod and ble of confining the flow and projects to a point weidable steel are examples of objects that can be an outside of said cavity; and chored within a cavity with expanding grouts and later adding into said cavity against said material capable fastened to additional articles. 50 of confining the flow and around a portion of said In fluid injection through a seal, the general method object, a hardenable and volume expandable non described above for anchoring objects within cavities is explosive demolition chemical grout material also employed, however, a tubular object is used. Em adapted to exert pressure and effect an expanded placement of the tubular object is such that both ends of seal upon curing between confining surfaces of the the tubular object protrude a substantial length from the 55 cavity, object and material capable of confining the expanding grout in which it is anchored. flow. The invention has been described in detailed specifics 6. The method of claim 5, wherein said wadding for purposes of illustration only, and it is to be under material capable of confining the flow of said grout is stood that many changes in the intracacies of use in selected from fabric, casing, foam rubber, rags and mining can be made without departing from the inven paper towels and said object is selected from threaded tion scope, which is defined by the appended claims. rods, high strength bolts, cables, and weldable steel. What is claimed: 7. The method of claim 6, wherein said chemical 1. A method of sealing a cavity such as a bore hole, grout is obtained by: admixing about 20% by weight of well, or fissure against passage of fluids without fractur water and about 80% by weight of a grouting composi ing walls of said cavity comprising: 65 tion composed of: placing in said cavity, a wadding material capable of confining the flow of a supply of hardenable and SiO2 0.6% volume expandable chemical grout which occupies Al2O3 0.5% 4,966,237 9 10 -continued object, a hardenable and volume non-explosive Fe2O3 1.6% demolition chemical grout material adapted to CaO. 89.1% exert pressure and effect an expanded seal upon MgO 1.7% curing between confining surfaces of the cavity, SO3 .01% (trace) conduit and material capable of confining the flow. Ignition Loss 6.5% 9. THe method of claim 8, wherein said wadding material of confining the flow of said grout is selected 8. A method of enabling the injection of fluid under from fabric, casing, foam rubber, rags and paper towels high pressure in a cavity such as a bore hole, well, or fissure without fracturing walls of said cavity, compris- 10 and said conduit is selected from high pressure tubing or ing: high pressure pipes. placing in said cavity, a wadding material capable of 10. The method of claim 8, wherein said chemical confining the flow of a supply of a hardenable and grout is obtained by: admixing about 20% by weight of volume expandable chemical grout which occupies water and about 80% by weight a grouting composition a given volume in its initial unhardened and unex 15 composed of: panded condition, and an increased volume in its hardened condition to exert an expansive force SiO2 0.6% against confining surfaces; Al2O3 0.5% placing a conduit capable of transmitting fluid under Fe2O3 1.6 high pressure within the cavity in a manner such 20 CaO 89.1% that said conduit extends through said material MgO 1.7% capable of confining the flow and projects to a SOs .01% (trace) point outside of said cavity; Ignition Loss 6.5% adding into said cavity against said material capable of confining the flow and around a portion of said 25

30

35

45

50

55

65